DATABASE MANAGEMENT SYSTEMS
TWO
MARKS:
INTRODUCTION
AND CONCEPTUAL MODELLING
1. Define database
management system?
Database management
system (DBMS) is a collection of interrelated data and a
set of programs to
access those data.
2. List any eight
applications of DBMS.
a) Banking
b) Airlines
c) Universities
d) Credit card
transactions
e) Tele communication
f) Finance
g) Sales
h) Manufacturing
i) Human resources
3. What are the disadvantages of file processing system?
The disadvantages of
file processing systems are
a) Data redundancy
and inconsistency
b) Difficulty in
accessing data
c) Data isolation
d) Integrity problems
e) Atomicity problems
f) Concurrent access
anomalies
4. What are the advantages of using a DBMS?
The advantages of
using a DBMS are
a) Controlling
redundancy
b) Restricting
unauthorized access
c) Providing multiple
user interfaces
d) Enforcing
integrity constraints.
e) Providing backup
and recovery
5. Give the levels of data abstraction?
a) Physical level
b) logical level
c) view level
6. Define instance and schema?
Instance: Collection
of data stored in the data base at a particular moment is
called an Instance of
the database.
Schema: The overall
design of the data base is called the data base schema.
7. Define the terms 1) physical schema 2) logical schema.
Physical schema: The
physical schema describes the database design at the physical level, which is the lowest level of
abstraction describing how the data are actually
stored.
Logical schema: The
logical schema describes the database design at the logical level, which
describes what data are stored in the database and what relationship exists among the data.
8. What is conceptual schema?
The schemas at the
view level are called subschemas that describe different views of the database.
9. Define data model?
A data model is a
collection of conceptual tools for describing data, data relationships, data
semantics and consistency constraints.
10. What is
storage manager?
A storage manager is
a program module that provides the interface between the low level data stored in a database and the
application programs and queries submitted to the system.
11. What are the
components of storage manager?
The storage manager
components include
a) Authorization and
integrity manager
b) Transaction
manager
c) File manager
d) Buffer manager
12. What is the
purpose of storage manager?
The storage manager
is responsible for the following
a) Interaction with
he file manager
b) Translation of DML
commands in to low level file system commands
c) Storing,
retrieving and updating data in the database
13. List the data structures
implemented by the storage manager.
The storage manager
implements the following data structure
a) Data files
b) Data dictionary
c) indices
14. What is a
data dictionary?
A data dictionary is
a data structure which stores meta data about the structure of the database ie. the schema of the database.
15. What is an
entity relationship model?
The entity
relationship model is a collection of basic objects called entities and relationship among those objects. An entity is
a thing or object in the real world that is distinguishable from other objects.
16. What are
attributes? Give examples.
An entity is
represented by a set of attributes. Attributes are descriptive properties possessed by each member of an entity set.
Example: possible
attributes of customer entity are customer name, customer id, customer street, customer city.
17. What is
relationship? Give examples
A relationship is an
association among several entities.
Example: A
depositor relationship associates a customer with each account that he/she has.
18. Define the
terms
i) Entity set
The set of all entities of the
same type is termed as an entity set.
ii) Relationship set
The set of all relationships of
the same type is termed as a relationship set.
19. Define
single valued and multivalued attributes.
Single valued attributes: attributes with a single value for a
particular entity are called single valued attributes.
Multivalued attributes: Attributes
with a set of value for a particular entity are called multivalued attributes.
20. What are
stored and derived attributes?
Stored attributes: The attributes stored in a data base
are called stored attributes.
Derived attributes: The attributes
that are derived from the stored attributes are called derived attributes.
21. What are
composite attributes?
Composite attributes can be
divided in to sub parts.
22. Define null
values.
In some cases a particular entity
may not have an applicable value for an attribute or if we do not know the
value of an attribute for a particular entity. In these cases null value is
used.
23. Define the
terms
i) Entity type
An entity type defines a
collection of entities that have the same attributes.
ii) Entity set
The set of all entities of the
same type is termed as an entity set.
24. What is
meant by the degree of relationship set?
The degree of relationship type
is the number of participating entity types.
25. Define the
terms
i) Key attribute
ii) Value set
Key attribute: An entity type
usually has an attribute whose values are distinct from each individual entity
in the collection. Such an attribute is called a key attribute.
Value set: Each simple
attribute of an entity type is associated with a value set that specifies the
set of values that may be assigned to that attribute for each individual entity.
26. Define weak
and strong entity sets?
Weak entity set: entity set that
do not have key attribute of their own are called weak entity sets.
Strong entity set: Entity set
that has a primary key is termed a strong entity set.
27. What does
the cardinality ratio specify?
Mapping cardinalities or
cardinality ratios express the number of entities to which
another entity can be associated.
Mapping cardinalities must be one of the following:
1.
One
to one
2.
One
to many
3.
Many
to one
4.
Many
to many
5.
28. Explain the
two types of participation constraint.
Total: The participation
of an entity set E in a relationship set R is said to be total if every
entity in E participates in at least one relationship in R.
Partial: if only some
entities in E participate in relationships in R, the participation of entity
set E in relationship R is said to be partial.
29. Define the
terms
i)DDL
ii)
DML
DDL: Data base schema
is specified by a set of definitions expressed by a special language called a
data definition language.
DML: A data
manipulation language is a language that enables users to access or manipulate
data as organized by the appropriate data model.
30. Write short
notes on relational model
The relational model uses a
collection of tables to represent both data and the relationships among those
data. The relational model is an example of a record based model.
31. Define tuple
and attribute
Attributes: column
headers
Tuple: Row
32. Define the term relation.
Relation is a subset of a
Cartesian product of list domains.
33. Define tuple
variable
Tuple variable is a variable
whose domain is the set of all tuples.
34. Define the
term Domain.
For each attribute there is a set
of permitted values called the domain of that attribute.
35. What is a
candidate key?
Minimal super keys are called candidate
keys.
36. What is a
primary key?
Primary key is chosen by the
database designer as the principal means of identifying an entity in the entity set.
37. What is a
super key?
A super key is a
set of one or more attributes that collectively allows us to identify uniquely
an entity in the entity set.
38. Define-
relational algebra.
The relational algebra is a
procedural query language. It consists of a set of operations that take one or two relation as
input and produce a new relation as output.
39. What is a
SELECT operation?
The select operation
selects tuples that satisfy a given predicate. We use the
lowercase letter to denote selection.
40. What is a
PROJECT operation?
The project operation is a unary
operation that returns its argument relation with
certain attributes left out.
Projection is denoted by pie ().
Definition for Implication (_):
P_Q means if P is true then Q
must be true.
42. Write short
notes on domain relational calculus
The domain relational calculus
uses domain variables that take on values from an attribute domain rather than
values for entire tuple.
43. Define query
language?
A query is a statement requesting
the retrieval of information. The portion of DML that involves information
retrieval is called a query language.
44. Write short
notes on Schema diagram.
A database schema along with
primary key and foreign key dependencies can be depicted pictorially by schema
diagram. Each relation appears as a box with attributes listed inside it and
the relation name above it.
45. What is
foreign key?
A relation schema r1 derived from
an ER schema may include among its attributes the primary key of another
relation schema r2.this attribute is called a foreign key from r1
referencing r2.
UNIT: 2
RELATIONAL MODEL
1. What are the parts of SQL language?
The SQL language has several parts:
data - definitition language
Data manipulation language
View definition
Transaction control
Embedded SQL
Integrity
Authorization
2. What are the categories of SQL command?
SQL commands are divided in to the following categories:
1. data - definitition language
2. data manipulation language
3. Data Query language
4. data control language
5. data administration statements
6. transaction control statements
3. What are the three classes of SQL expression?
SQL expression consists of three clauses:
Select
From
where
4. Give the general form of SQL query?
Select A1, A2…………., An
From R1, R2……………, Rm
Where P
5. What is the use of rename operation?
Rename operation is used to rename both relations and a attributes.
It uses the as clause, taking the form:
Old-name as new-name
6. Define tuple variable?
Tuple variables are used for comparing two tuples in the same relation. The tuple variables are defined in the from clause by way of the as clause.
7. List the string operations supported by SQL?
1) Pattern matching Operation
2) Concatenation
3) Extracting character strings
4) Converting between uppercase and lower case letters.
8. List the set operations of SQL?
1) Union
2) Intersect operation
3) The except operation
9. What is the use of Union and intersection operation?
Union: The result of this operation includes all tuples that are either in r1 or in r2 or in both r1 and r2.Duplicate tuples are automatically eliminated.
Intersection: The result of this relation includes all tuples that are in both r1 and r2.
10. What are aggregate functions? And list the aggregate functions supported by SQL?
Aggregate functions are functions that take a collection of values as input and return a single value.
Aggregate functions supported by SQL are
Average: avg
Minimum: min
Maximum: max
Total: sum
Count: count
11. What is the use of group by clause?
Group by clause is used to apply aggregate functions to a set of tuples. The attributes given in the group by clause are used to form groups.Tuples with the same value on all attributes in the group by clause are placed in one group
.
12. What is the use of sub queries?
A sub query is a select-from-where expression that is nested with in another query. A common use of sub queries is to perform tests for set membership, make set comparisions, and determine set cardinality.
13. What is view in SQL? How is it defined?
Any relation that is not part of the logical model, but is made visible to a user as a virtual relation is called a view.
We define view in SQL by using the create view command. The form of the create view command is
Create view v as <query expression>
14. What is the use of with clause in SQL?
The with clause provides a way of defining a temporary view whose definition is available only to the query in which the with clause occurs.
15. List the table modification commands in SQL?
Deletion
Insertion
Updates
Update of a view
16. List out the statements associated with a database transaction?
Commit work
Rollback work
17. What is transaction?
Transaction is a unit of program execution that accesses and possibly updated various data items.
18. List the SQL domain Types?
SQL supports the following domain types.
1) Char(n) 2) varchar(n) 3) int 4) numeric(p,d)
5) float(n) 6) date.
19. What is the use of integrity constraints?
Integrity constraints ensure that changes made to the database by authorized users do not result in a loss of data consistency. Thus integrity constraints guard against accidental damage to the database.
20. Mention the 2 forms of integrity constraints in ER model?
Key declarations
Form of a relationship
21. What is trigger?
Triggers are statements that are executed automatically by the system as the side effect of a modification to the database.
22. What are domain constraints?
A domain is a set of values that may be assigned to an attribute .all values that appear in a column of a relation must be taken from the same domain.
23. What are referential integrity constraints?
A value that appears in one relation for a given set of attributes also appears for a certain set of attributes in another relation.
24. What is assertion? Mention the forms available.
An assertion is a predicate expressing a condition that we wish the database always to satisfy.
Domain integrity constraints.
Referential integrity constraints
25. Give the syntax of assertion?
Create assertion <assertion name>check<predicate>
26. What is the need for triggers?
Triggers are useful mechanisms for alerting humans or for starting certain tasks automatically when certain conditions are met.
27. List the requirements needed to design a trigger.
The requirements are
Specifying when a trigger is to be executed.
Specify the actions to be taken when the trigger executes.
28. Give the forms of triggers?
The triggering event can be insert or delete.
For updated the trigger can specify columns.
The referencing old row as clause
The referencing new row as clause
The triggers can be initiated before the event or after the event.
29. What does database security refer to?
Database security refers to the protection from unauthorized access and malicious destruction or alteration.
30. List some security violations (or) name any forms of malicious access.
Unauthorized reading of data
Unauthorized modification of data
Unauthorized destruction of data.
31. List the types of authorization.
Read authorization
Write authorization
Update authorization
Drop authorization
32. What is authorization graph?
Passing of authorization from one user to another can be represented by an authorization graph.
33. List out various user authorization to modify the database schema.
Index authorization
Resource authorization
Alteration authorization
Drop authorization
34. What are audit trails?
An audit trail is a log of all changes to the database along with information such as which user performed the change and when the change was performed.
35. Mention the various levels in security measures.
Database system
Operating system
Network
Physical
human
36. Name the various privileges in SQL?
Delete
Select
Insert
update
37. Mention the various user privileges.
All privileges directly granted to the user or role.
All privileges granted to roles that have been granted to the user or role.
38. Give the limitations of SQL authorization.
The code for checking authorization becomes intermixed with the rest of the application code.
Implementing authorization through application code rather than specifying it declaratively in SQL makes it hard to ensure the absence of loopholes.
39. Give some encryption techniques?
DES
AES
Public key encryption
40. What does authentication refer?
Authentication refers to the task of verifying the identity of a person.
41. List some authentication techniques.
Challenge response scheme
Digital signatures
Non repudiation
42. Define Boyce codd normal form
A relation schema R is in BCNF with respect to a set F of functional dependencies if, for all functional dependencies in F+ of the form. α->β.
43. List the disadvantages of relational database system
Repetition of data Inability to represent certain information.
44. What is first normal form?
The domain of attribute must include only atomic (simple, indivisible) values.
45. What is meant by functional dependencies?
Consider a relation schema R and α C R and β C R. The functional dependency α β holds on relational schema R if in any legal relation r(R), for all pairs of tuples t1 and t2 in r such that t1 [α] =t1 [α], and also t1 [β] =t2 [β].
46. What are the uses of functional dependencies?
To test relations to see whether they are legal under a given set of functional dependencies.
To specify constraints on the set of legal relations.
47. Explain trivial dependency?
Functional dependency of the form α β is trivial if β C α. Trivial functional dependencies are satisfied by all the relations.
48. What are axioms?
Axioms or rules of inference provide a simpler technique for reasoning about functional dependencies.
49. What is meant by computing the closure of a set of functional dependency?
The closure of F denoted by F+ is the set of functional dependencies logically implied by F.
50. What is meant by normalization of data?
It is a process of analyzing the given relation schemas based on their Functional Dependencies (FDs) and primary key to achieve the properties
Minimizing redundancy
Minimizing insertion, deletion and updating anomalies.
51. Define canonical cover?
A canonical cover Fc for F is a set of dependencies such that F logically implies all dependencies in FC and Fc logically implies all dependencies in F. Fc must have the following properties.
52. List the properties of canonical cover.
Fc must have the following properties.
No functional dependency in Fc contains an extraneous attribute. Each left side of a functional dependency in Fc is unique.
53. Explain the desirable properties of decomposition.
Lossless-join decomposition
Dependency preservation
Repetition of information
54. What is 2NF?
A relation schema R is in 2NF if it is in 1NF and every non-prime attribute A in R is fully functionally dependent on primary key.
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